Set Expires headers for Hydra's binary cache

This allows caching by reverse proxies.

src/lib/Hydra/Controller/Root.pm

@@ -244,6 +244,7 @@ sub nix_cache_info :Path('nix-cache-info') :Args(0) {
         # Give Hydra binary caches a very low priority (lower than the
         # static binary cache http://nixos.org/binary-cache).
         "Priority: 100\n";
+    setCacheHeaders($c, 365 * 24 * 60 * 60);
     $c->forward('Hydra::View::Plain');
 }
 
@@ -260,6 +261,7 @@ sub narinfo :LocalRegex('^([a-z0-9]+).narinfo$') :Args(0) {
         $c->response->content_type('text/plain');
         $c->stash->{plain}->{data} = "does not exist\n";
         $c->forward('Hydra::View::Plain');
+        setCacheHeaders($c, 60 * 60);
         return;
     }
 

src/lib/Hydra/Helper/CatalystUtils.pm

@@ -28,6 +28,7 @@ our @EXPORT = qw(
     showJobName
     showStatus
     getResponsibleAuthors
+    setCacheHeaders
 );
 
 
@@ -305,4 +306,12 @@ sub getResponsibleAuthors {
 }
 
 
+# Set HTTP headers for the Nix binary cache.
+sub setCacheHeaders {
+    my ($c, $expiration) = @_;
+    $c->response->headers->expires(time + $expiration);
+    delete $c->response->cookies->{hydra_session};
+}
+
+
 1;

src/lib/Hydra/View/NARInfo.pm

@@ -5,6 +5,7 @@ use base qw/Catalyst::View/;
 use File::Basename;
 use Nix::Store;
 use Nix::Crypto;
+use Hydra::Helper::CatalystUtils;
 
 sub process {
     my ($self, $c) = @_;
@@ -39,6 +40,8 @@ sub process {
         $info .= "Signature: 1;$keyName;$sig\n";
     }
 
+    setCacheHeaders($c, 24 * 60 * 60);
+
     $c->response->body($info);
 
     return 1;

src/lib/Hydra/View/NixNAR.pm

@@ -2,6 +2,7 @@ package Hydra::View::NixNAR;
 
 use strict;
 use base qw/Catalyst::View/;
+use Hydra::Helper::CatalystUtils;
 
 sub process {
     my ($self, $c) = @_;
@@ -14,6 +15,8 @@ sub process {
 
     open $fh, "nix-store --dump '$storePath' | bzip2 |";
 
+    setCacheHeaders($c, 365 * 24 * 60 * 60);
+
     $c->response->body($fh);
 
     return 1;